/*
 * Alloy Analyzer
 * Copyright (c) 2002 Massachusetts Institute of Technology
 *
 * The Alloy Analyzer is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * The Alloy Analyzer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with the Alloy Analyzer; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package alloy.util;

import java.lang.ref.SoftReference;

/**
 * A one-object memory-sensitive cache that automatically regenerates
 * the cached object if it gets garbage-collected.
 */
public class Regenerator {
    /** A {@link SoftReference} to the object we're storing. */
    private SoftReference _ref;

    /** The generator we use for reconstructing garbage-collected objects. */
    private ObjGenerator _gen;

    public Regenerator(ObjGenerator gen_) {
	_gen = gen_;
    }

    public Object get() {
	if (_ref == null)
	    _ref = new SoftReference(_gen.generate());
	Object cachedObj = _ref.get();
	if (cachedObj == null)
	    _ref = new SoftReference(cachedObj = _gen.generate());
	return cachedObj;
    }
}




